Preparation of cyclo-trimethylenetrinitramine



Patented Feb. 26, 1946 PREPARATION on CYCLO-TRIMETHYL- ENETRINITBAMINE Joseph A. Wyler, Allentown, Pa., assignor to Trojan Powder Company, Allentown, Pa.

No Drawing. Application November 20, 1942,

Serial No. 466,383

4 Claims.

This invention relates to the nitration of hexamethylenetetramine to cyclo-trimethylenetrinitramine, commonly called Hexogen or Cyclonite.

It is well known that hexamethylenetetramine can be nitrated to cyclo-trimethylenetrinitramine by means of concentrated nitric acid. However, the best yields obtainable to date, so far as I am aware, are in the neighborhood of 70% of theory.

It is an object of my invention to prepare cyclo trimethylenetrinitramine from hexamethylenetetramine in substantially greatei yields; another object is to provide a process of nitration of hexamethylenetetramine to cyclotrimethylenetrinitramine which may be carried out at higher and more practicable temperatures than those found necessary'for the best yields to date; and, a further object is to provide a process for the nitration of hexamethylenetetramine in which the tendency for spontaneous decomposition is greatly reduced. Other and further objects will become apparent upon a perusal of this specification.

I have discovered that the addition of ammonium salts such as NHQNOB and (NI-102804 to concentrated HNOs produces a nitrating mixture which is particularly well adapted to the nitration of hexamethylenetetramine. The most significant effects of this addition are an important improvement in the yield of cyclotrimethylenetrinitramine obtained from a given weight of hexamethylenetetramine and an ine crease in the safety of the nitration. Thus, I have found that if hexamethylenetetramine is added to, say 98% HNOz and the reaction mixture handled under well known conditions, which give a yield of cyclo-trimethylenetrinitramine of say, 65-70% of theory, the addition of certain ammonium salts to this identical 98% ENG: will produce a nitration mixture, which, when used in the same manner as the original 98% HNOa will give a yield of cyclo-trimethylenetrinitramine of over of theory.

In order more clearly to point out my invention, the following examples in which all parts are by weight, are given.

Example #1 hexamethylenetetramine, the mixture was stirred for about 5 minutes, and drowned in about 3000 parts of ice and water. The precipitated cyclo-trimethylenetrinitramine was filtered off, washed with cold water, then with hot water, dried and weighed. The yield'was more than of theory.

Using the same nitric acid without the addition of the ammonium nitrate the yield was about 65% of theory.

Example #2 parts of NH4NO3, with stirring, at-3 C. to 10 C.

The period of addition was 55 minutes and the additional stirring lasted for 15 minutes. The reaction mixture was drownedandhandled in the manner described Example 1. The yield of cyclo-trimethylenetrinitramine obtained was 94 parts or about of theory. The proportion of the hexamethylenetetramine to NH4NO3 in this example is one to 0.36, or about 8 to 3.

Emmple #3 Using 75 parts of ammonium nitrate in place of the 25 parts of the previous example, the

yield of cyclo-trimethylenetrinitramine obtained Using parts of ammonium nitrate in place of the 25 parts of the previous example, the yield of cyclo-trimethylenetrinitramine obtained was only 60% of theory, indicating that this proportion of NI-I4NO3 to HNO3 is too high.

Example #5 of theory. This amount of (NI-1432304 is equiv alent to about 12.9 parts NI-I3 to 858 parts of 100% HNOs or 1 part NI-Is per 66.5 parts of 100% HN 3- Example #6 Using 75 gms. of ammonium sulfate instead of the 50 gms. in Example #5, a yield of only 70 parts or about 63% of theory was obtained, indicating that this proportion, 1 part NH3 per 44 parts 100% HNOa is too much.

Example #7 Using 100 gms. of ammonium sulfate and proceeding in the same manner as in Example #6 gave a yield of only 61% of theory.

It will be noted that I may use nitric acid of any strength capable of converting hexamethylenetetramine to cyclo-trimethylenetrinitramine, that is, any strength above, about 80% HNOa. In this specification, the term concentrated nitric acid is used for any nitric acid of about 80% or more I-INO3 content.

Also, I may vary the proportion of hexa methylenetetramine to HNO3 over a wide range. I prefer, however, a ratio of 8 parts hexamethylenetetramine to 100 parts of HNO3. I may use any temperature of nitration from below C. to about 50 0., although I prefer to use the range of about C. to about 30 0., and I may use a mixture of the ammonium salts mentioned above provided the total NHs content of the added mixture does not exceed about 1 part of NH: for about 50 parts of 100% HNO3.

I wish to emphasize that the amount of ammonium salts usedin my process should not exceed a critical upper limit. This limit varies somewhat with the temperature of nitration and-- strength of the nitric acid used. I consider the limit as being not more thanabout 1 part of NH3 equivalent of the ammonium salt used per 50 parts of 100% HNOs. If more than this amount of ammonium salts is used the yield of cyclo-trimethylenetrinitramine obtained is lessened.

It should also be noted that a small amount of ammonium nitrate is formed in the normal nitration of hexamethylenetetramine with I-INO: and that the present invention is intended to cover a process of nitration in which an added amount of NHiNOS or (NI-M2804 is present in the nitrating acid, the ammonium salts being added before or during the addition of the hexamethylenetetramine to the nitrating bath.

Also, ammonium nitrate when present in the nitrating acid as the latter is being poured into water to precipitate the cyclo-trimethylenet'rinitramine prevents the usual rise in temperature and in this respect produces an additional, useful result.

Also, the presence of ammonium nitrate or ammonium sulfate in the nitrating bath lessens the tendency for decomposition in the bath and permits a higher temperature to be used for the nitration. This in itself is an important contribution since the literature upon the nitration of hexamethylenetetramine has shown that the nitration often becomes uncontrollable and the bath must then be prematurely discharged into water to avoid serious accident. This tendency for decomposition is exceptionally great because of the formation of CH2O from the methylene groups within the hexamethylenetetramine ring and the relative ease with which CH2O is attacked by concentrated nitric acid.

The function performed by the ammonium salts mentioned is not known, but it is known that all ammonium salts do not improve the yield of cyclo-trimethylenetrinitramine. Thus, for example, the addition of ammonium chloride does not cause any improvement in yield. It is believed that the function of the added ammonium salts is to alter the nature of the forces binding the water which is liberated during the nitration and this in turn partially prevents the hydrolysis of the hexamethylenetetramine to CHzO. I wish to emphasize that this theory is presented merely for purposes of clarity and completeness and is not intended to limit my invention in any way not indicated by the appended claims.

l. The process for the nitration of hexamethylenetetramine to cyclotrimethylenetrinitramine which comprises reacting hexamethylenetetramine with concentrated nitric acid containing an added amount of an ammonium salt selected from the group consisting of ammonium nitrate and ammonium sulfate at a nitrating temperature; said amount of ammonium salt being not more than the equivalent of about one part by weight of NH3 per 50 parts of HNOs; adding the reaction mixture, with stirring, to an excess of cold water and filtering off the cyclotrimethylenetrinitramine which precipitates.

2. The process for the nitration of hexamethylenetetramine to cyclotrimethylenetrinitramine which comprises adding hexamethylenetetramine, with stirring, to a concentrated nitric acid at a temperature of less than 50 C., said nitric acid containing an added amount of an ammonium salt selected from the group consisting of ammonium nitrate and ammonium sulfate, said amount of ammonium salt being not more than the equivalent of about one part (by weight) of NH3 per 50 parts of 100% HNO3; adding the reaction mixture, with stirring, to an excess of cold water, filtering ofi the cyclo-trimethylenetrinitramine, washing the latter with water and dry- 111g.

3. The process for the nitration of hexamethylenetetramine to cyclotrimethylenetrinitramine which comprises adding, with stirring, about 8 parts, by weight, of hexamethylenetetramine to about 100 parts, by weight, of about 98% HNOa,

at a temperature between about 5 C. and 30 0.; said nitric acid containing in solution an added ammonium salt selected from the group consisting of ammonium nitrate and ammonium sulfate, such addition being in an amount not greater'than the equivalent of about one part (by weight) of NH3 per 50 parts of 100% HNOa; adding the nitration mixture, with stirring, to an excess of cold water, filtering off the cyclo-trimethylenetrinitramine, washing the latter with water and drying.

4. The process for the nitration of hexamethylenetetramine to cyclotrimethylenetrinitramine which comprises adding, with stirring, about 8 parts, by weight, of hexamethylenetetramine to about 100 parts, by weight, of about 98% HNO3, at a temperature between about 5 C. and 30 C. said nitric acid containing in solution about 3 parts,'by weight, of added ammonium nitrate; adding the nitration mixture, with stirring, to an excess of cold water, filtering off the cyclo-trimethylenetrinitramine, washing the latter with water and drying.

, JOSEPH A. WYLER. 

